Conventionally, a position detector has been known to detect a position of a detection body, such as an angle of rotation of a throttle valve of a vehicular electronic control throttle device, an angle of rotation of an accelerator pedal of an accelerator pedal module, the amount of stroke of a clutch actuator and the like. For example, a position detector detects the angle of rotation or the amount of stroke of a detection body such as a throttle valve by detecting a magnetic field generated from a magnet attached to the detection body using a magnetic detection IC such as a Hall IC. It is to be noted that the magnetic detection IC is an electronic component into which a magnetic field detection element and an integrated circuit for processing a signal outputted from the magnetic field detection element are integrated.
For example, U.S. Pat. No. 7,369,969 B2 describes a position detector. In the position detector described, a signal transmitted from a magnetic detection element and passing through an analog-to-digital (A/D) converter circuit is processed at a digital signal processor (DSP), and the signal processed is outputted to an external device via a digital-to-analog (D/A) converter circuit. Further, a memory is disposed between the DSP and the D/A converter circuit to store data outputted from the DSP. Moreover, monitoring circuits are provided to monitor instantaneous interruption of electric power supply to each of the circuits.
When the monitoring circuit detects the instantaneous interruption of the electric power supply to the A/D converter circuit or the DSP, the memory stops updating of the data, holds the data stored immediately before the instantaneous interruption of the electric power supply, and outputs the data to the external device through the D/A converter circuit. Therefore, the position detector keeps normal output when the instantaneous interruption of the electric power supply occurs.
In the position detector of U.S. Pat. No. 7,369,969 B2, however, the memory is disposed between the A/D converter circuit and the D/A converter circuit. Therefore, if a malfunction occurs in the memory due to deterioration of the memory or the like, it is concerned that the position detector will not ensure desired output behavior.